Electrode mounting device



Feb. 13, 1951 P. GIUFFRIDA 2,541,236

ELECTRODE MOUNTING DEVICE Filed June 8, 1948 2 SheetsSheet l 44 396846 59 22 ii a 3 WY W 45 48 I, s3 29 j 43 55 I PHIL IP GlUFFR/DA lnvenfnr' the reliability of the associated with the flame understood from the Patented Feb. 13, 1951 2,541,236 ELECTRODE MOUNTING DEVICE Philip Giuflrida,

Lawrence, Mass" as'signor to Combustion Control Corporation, Cambridge, Mass., a corporation of Massachusetts Application June 8, 1948, Serial No. 31,659

This invention relates to apparatus for mounting a flame detection electrode on a furnace.

Automatic and semi-automatic furnaces, burning volatile fuels are generally equipped with a flame failure safeguard which operates to shut off theiuel supply, and so prevent explosion, ii the burner fails to ignite properly or if the flame accidentally becomes extinguished. One type of flame failure control employs as a detecting element an electrode, or flame rod, which establishes an electrical contact with the flame, thus completing an electrical circuit which operates in connection with associated electrical apparatus to control the fuel supply. The electrode is held in an insulating mounting on the furnace wall. Because of the serious hazards involved,

especially in burners of the large industrial types, flame failure device is oi utmost importance. The flame rod type of detector and its insulator are necessarily exposed to the combustion chamber and eventually accumulate a deposit of soot. Safe operation of the flame failure control can be insured by so designing the circuit that excessive loss of resistance between the flame rod and ground, due to soot deposit on the flame failure and results in a shut-down. The control then prevents operation of the burner until the flame rod insulation is cleaned. Such a circuit is ing application to E. C. Thomas, Serial No. 754,435, filed June 13, 1947, Flame Failure Safeguard. Since such a shut-down may occasion considerable inconvenience and expense, however, it is desirable to delay the accumulation of soot and prolong the satisfactory operation of the flame rod as much as possible. The rod must also be protected against short circuiting or accidental contacts which might, under certain conditions, maintain operation of the fuel supply in the absence of flame. It may also be advantageous in some installations to mount certain electrical components of the control circuit such as an amplifier tube, as close to the flame electrade as possible, in which case, the component must be protected against excessive heat.

The object of this invention is, accordingly, to provide an electrode mounting device which protects the flame electrode from accidental contact, which maintains adequate insulating between the electrode and the furnace wall over long periods of operation, amplifier tube and other electrical components rod circuit, which permits ready access-for cleaning and inspecting, and which is simple, durable, compact, and easily installed.

These and other advantages and novel features of the mounting device will be more readily following description. In the accompanying drawings:

insulation, is equivalent to.

described, for example in co-pendwhich may house an 12 Claims. (oi, 114-52) Fig. 1 is a side elevation of the device;

Fig. 2 is a partial cross-section along lines 2-2 of Fig. 1;

Fig. 3 is a view along lines Fig. 4 is a plan view of housing cover removed;

Fig. 5 is a partial cross-section along. lines 2-2 of Fig. 1 showing the interior of the housing arranged for mounting on amplifier tube.

As illustrated in Figs. 1, 2 and 4, a housing consisting of base 10 and cover H is secured to a mounting flange l8 by three screws I9 which extend through spacers l1 and are threaded into bosses IS. The mounting flange I8 is provided with a recess 22 which slides over a piece of pipe 23, the other end of which is welded into the wall of the furnace (not shown) in which the flame electrode is to be mounted. Flange I8 is prevented from turning on the pipe 23 by set screws 1. Cover II is secured to base In by screws 50. A

3-3 of Figs. 2 and 4'; the device with the gasket I5 is ordinarily provided between lips l3 and H of cover H and base ll! respectively. The flame rod assembly is secured to the vertical inner face of base 10 by screws 32 which extend through insulating spacers 35, 31 38 into tapped holes in the housing. A guard plate 34 is secured by rivets to spacer 38, Mounted on either side of plate 34, and separated from it by compressible gaskets 5| are ceramic insulators 21 and 28. A boss 54 on insulator 28 extends into recess 55 in 'insulator 21. A stud 43, of brass or other metal of good conductivity, extends through insulators 21 and 28. On its inner threaded end, stud 43 carries sealing washer 52, contact bracket 39, lock washer 56, nut 48, contact lug '42, and nut 41. Mounted on the outer threaded end of stud 43 are sealing washer 43, baflie plate 33, lock washer 51 and chuck 20. In assembling the insulators and other parts onto the rod, a heat resistant cement is preferably applied between adjoining faces. When nut 48 is tightened, the entire assembly is held securely on guard plate 34. Nut 41 may be removed and replaced as required for wiring purposes.

The outer end of chuck 20 is recessed to receive the flame rod 21, which is a piece of rod of conductive material such as nickel steel cut to any required length. The rod is secured by set screw 29. A fin 26 is inserted between bosses l6 and spacers H to dissipate the heat conducted through pipe 23 and flange 18 from the furnace wall. Between the housing and the mounting flange, the rod assembly is surrounded by a heat resistant glass shield 58. The inner endof the shield rests against gasket 59, held in place by boss 61 on the housing, and the outer end presses against gasket mounted in recess 64 in the flange. The shield protects the rod assembly, between the housing and the mounting flange, from dirt, accidental contact, and tampering, and, at the same time, permits visual inspection 3 of the insulation. mange I8 is thickened on its underside to accommodate clean-out hole I! to which an air hose may be applied for blowing soot oi! the flame rod insulation. Where required, an air hose may be permanently attached for-cooling. When the hole is not in use it is closed by lug 24.

p It will be noted that the insulation of the flame rod does not touch any part of the housing but is in contact only with guard plate 34. Consequently any leakage current due to soot, dirt or moisture deposits on the surface 01' the insulation will flow between the rod and guard plate rather than the rod and ground. In order to minimize such leakage, the insulators 21 and II are so constructed as to provide long internal and external surface paths between the rod and the guard plate and the more exposed insulator 21 is protected against blow-backs of soot by bai'lle 33. In the control circuit illustrated in the copending application to E. C. Thomson, previously referred to, the guard plate is so connected that either excessive leakage, or short circuit, between the rod and the guard ring will cause the burner to shut-down as on flame fallure. Provision is made in this device for employing this circuit characteristic to shut down the burner when the cover II is removed, so that the burner cannot be maintained in operation, or started by accidental contact between the inner end of the rod and some external conductive object, when the cover is 01!. For this Purpose, a leaf spring 46 is riveted to the guard plate. The spring projects through slot 6| in contact bracket 39 and carries, on its free end, insulating button 44 fastened by screw 45. when cover II is in place, it presses against button II and pushes spring 46 out of contact with bracket 39. When the cover is removed, spring 48 engages bracket 39, and thus short circuits the guard plate to the flame rod. In Fig. 2, wire 61 of cable 62 is connected to the rodby terminal washer 42. The guard plate terminates in a bracket 69, to which the shield 66 oi cable 62 is fastened by cable clamp 49. The cable runs through a conventional connector 3| mounted in one of the holes 39.

Fig. 5 shows the housing adapted for mounting amplifier tube I4, and other electrical components of suitable size. A chassis I3 is secured to housing base I 0 by screws 15 and 16. A terminal board is supported by chassis 13 and straps 11 which are secured to the upper pair of screws'32 and clear guard ring 3! and button 44. Nut 41 and lug 42 are omitted. Bracket 39 is provided with an extension 65 to which internal wiring connections to the rod are made. A flat guard plate 34 is used. In other respects, the embodiment of Fig. 5 is the same as that of Fig. 2.

Since certain changes may be made in the above-described article and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not in a limiting sense.

What is claimed:

1. An electrode mounting device comprising: a housing; spaced from, said housing; an insulating spacer attached to said housing; a conductive plate a mounting flange connected to, but

and said'flangc.

3. Adevice ccordin toclalmiihavlngacoollngnnmounte betweensaidhousingandsaid l se.

ccordin to claim 2 having a bafthe outer end of said rod toward, but

from the walls oi, the recess: a conductive rod extending through said bushings; and means carried by said rod for clamping said to gether against said plate thereby supporting the entire rod and bushing assembly on said plate.

12. A device according to claim 11 wherein the inner surface of said bushings is spaced ,from the outer surface of said rod.

PHILIP GIUFFRIDA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 11,759 Poche July 11, 1899 2,077,294 White Apr. 13, 1937 2,434,924 Hamilton Jan. 27. 1948 2,448.49! Rosche Aug. 31, 1948 

